Input Impendence at the sinking end of 9264 Module

[UPRR]

Hi,

I want to use NI 9264 to trigger two variable frequency signals i.e. 5-2000Hz and 0-2000Hz to my PLC Input card and Input impedence of two of PLC inputs are 860 Ohms and 8K Ohms respectively.

Please confirm whether NI 9264 is good on these parameters of input card.

Thanks

Prashant

[Tushar_Jambhekar]

as per the specifications at http://sine.ni.com/nips/cds/view/p/lang/en/nid/209896

each analog output in the card can supply max 4 mA current (but total is not more than 16mA) assuming you are not using more than 4 channels

the minimum load turns out to be 2.5K ohm for 10V. hence your 860 ohm input will not work. but 8 k might work.

However i doubt that the PLC input impedances you are talking are wrong. generally input impedances are very high for analog inputs.

Also you should consult NI representative and PLC vendor before finalizing any decision.

[UPRR]

Hi,

If I put some resistors at the input end of my PLC card and make 860 Ohms to 2.5k Ohms. Will that work?

Thanks

Prashant

[A_Donfigulation_Error_Has]

Hi Prashant,

Fine tuning the input impedance of your PLC device by putting a resistor in series may not be the best thing to do. In general, modifying a device to operate differently than the way it was designed may not operate as exected. Do you by any chance have the device spec sheets or device model of the PLC's you are trying to use?

Jason L.

[UPRR]

Hey Jason,

These are the  parameters of the PLC inputs:

Passive tachometer input:

 Operating Frequency Range 5Hz to 2000Hz

 Sensitivity: 250mV p-p

 Safe operating range: 0-100Vp-p

 Input impedance: 8k Ohms

 Accuracy: 0.1%

Active tachometer input:

 Operating Frequency Range 0Hz to 2000Hz

 Sensitivity: 7V

Safe operating range: 0-15V

 Input impedance: 860 Ohms

 Accuracy: 0.1%

Please let me know if you more queries.

Thanks

Prashant

[Tushar_Jambhekar]

Putting resistor to reduce current may not be a good idea.

i would suggest you to use opamp based buffer. this will increase the current sourcing capability.

[Tushar_Jambhekar]

BTW are you using square wave as input or non square wave. Asking this question just because you are using analog output instead of timer/counter output.

[UPRR]

Hi,

I have total of 3 inputs and I will be using one sine wave and 2 square wave and will change the frequencies of the signals using Labview as my PLC behaves differently at different frequencies.

Thanks

Prashant